Treating steel



E.F!KENNEY.'

TREATING STEEL.

APPLICATION FILED NOV-20.1919.

1,334,379. Patented Mar. 23, 1920.

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EDWARD F. KENNEY, OF PHILADELPHIA, PENNSYLVANIA.

TREATING s'rnnn Specification of Letters Patent.

Patented Mar. 23, 1920.

Application filed November 20, 1919. Serial 1T0. $39,343.

To all whom it may concern:

Be it known that I, EDWARD F. KENNET, a citizen of the United States,and a resident of the city of Philadelphia, county of Ph11adelphia, andState of Pennsylvania, (whose post-ofiice address is Philadelphia,Pennsylvania,) have invented certain new and useful Improvements inTreating Steel; and I do hereby declarethe following to be a full,clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

My invention relates to the treatmentof steel with particular referenceto steel rails, which, after having been rolled in a rolling mill, areordinarily placed upon cooling beds and are cooled to atmospherictemperature. This practice results in first cooling the exteriorportions of the steel while the interior is hot, and as the hot interiorfurther cools the contraction thereof is resisted by the cooler andstifi'er exterior with the'result of setting up internal stresses whichmay afterward, in' use, add to the stresses of service and shorten thelife or usefulness of the rail.

Although my method of treatment may apply to any kind of rolled steelbars, forgings, etc., I will, for the sake of simplicity of description,confine the same to the treatment of rails, thereby making thephraseology herein more simple.

In conducting my process I roll the ra ls in the usual Way at atemperature permitting the plastic flow and deformation of the material,and, generally speaking, the rolling of the rails is finished when theycome out of the finishing passes at a good red heat, that is at anapproximate temperature of from N00 to 1900 degrees Fahrenheit. Therails heretofore have been then ordmar 1ly run through a camberingmachine to give them a certain amount of camber so that when they arecool they are approximately straight, the reason for the camberlng being that the thicker head portions cool last and unless the camber orcurve is given the rails would be crooked when cool.

On accountof contact with the metal rolls in the operation of rollingand also because of the cooling eifect of the atmosphere, the exteriorportions. of the rail 0001 more rapidly than the interior. I This isparticularly true of the head which is the thickest portion of. therail, and results in the interior of the head being red hot when theexterior is black hot. This difi'erence in temperature is continued asthe rail cools. As long as all the metal of the rail is plastic, no harmresults, but as soon as the exterior is cool enough to become rigid, itresists the shrinkage of the hotter interior. This resistance toshrinkage results in tensile stresses in the interior of the rail whichtend to shorten the life of the rail as previously mentioned.

In order to obviate this diiiiculty, after the rails have issued fromthe finishing passes of the rolls, I camber them, to a certain extent,and place them on a cooling bed and when the exterior of a rail hasreached a temperature of approximately 800 to 1000,degrees Fahrenheit, Iintroduce it into a furnace at a temperature of about 800 degreesFahrenheit, more or less, so that the outside is kept hot While theinside is cooling, thereby equalizing the temperature of the inner andouter portions and preventing the undue stresses above mentioned.

At a temperature of about 800 degrees Fahrenheit the material of therail is quite plastic or comparatively Weak and the interior andexterior portions can readily become harmonized with respect to theircooling, obviating difi'erences in stresses between the two portions.

The tensile strength of steel increases from ordinary atmospherictemperature up to about 500 degrees Fahrenheit, then sharply declines toabout 900 degrees Fahrenheit where it rises slightly and then as ,itbecomes hotter there is a very marked reduction in tensile strength.

Similarly the elastic limit of steel -from atmospheric temperaturedeclines gradually to about 800 degrees Fahrenheit, then increases veryslightly to about 900 degrees and then decreases very quickly as thetemperature is increased beyond 900 degrees. Therefore, the mostadvantageous temperature for equalizing the heat is between 500 and 1200degrees Fahrenheit, the exact temperature selected varying, however,with the carbon content of the steel, the contour of the rail and otherconditions. The elastic limit of rail steel at ditferent temperatures isplainly shown on diagram herewith which, with thelegends thereon, willbe readily read and understood and from which it can be seen that theelastic limit of zero Fahrenheit is about 60,000 pounds per square inchand at about 800 degrees Fahrenheit it is only 38,000 pounds per squareinch, and other figures for other temperatures.

In order to make sure that the rail may vbe straight without againsetting up un due stresses due to cold straightening, I also straightenthe rails between the temperatures of 500 and 1200 degrees Fahrenheit.The straightening of the rails in this manner may be done with either aroller or gag straightening press, but I prefer a roller straightener asthis will effect the results with less local stresses.

Although I have described and illustrated my invention in considerabledetail, I do not wish to be limited to the exact and specific detailsthereof as shown and described, but may use such' modifications in,substitutions for, or equivalents thereof, as are embraced within thescope of my invention,-or as pointed out in the claims.

Having thus described my invention,

what I claim and desire to secure by Let ters Patent is 2- 1. Theprocess of treating steel shapes which consists in finishing them in arolling mill at a red heat, then allowing the temperature to fall tobetween 500 degrees and 1200 degrees Fahrenheit, then substantiallyequalizing the heat of the different portions tween these temperatures,allowing them to remain in said furnace until all portions aresubstantially of the same temperature, then withdrawing them from saidfurnace and promptly straightening the same.

In witnesswhereof I hereunto affix my signature.

.EDWARD F. KENNEY.

